Origin AS field

During a request to ARIN Online for IP address block information, the Origin Autonomous System (AS) field is optional. This field is included in the ARIN Number Resource Policy Manual and is used by IP address block holders to record the list of ASNs they are responsible for. A list of these ASNs is recorded during all IPv4 and IPv6 block transactions. This information is important to ISPs because it can help them determine the validity of a Letter of Authority. It is also important for ISPs to know when an organization has changed its contact information. A network’s Origin AS field is limited to 256 results.

If you have a valid letter of authority, you can configure your Origin AS field to match your ISP. You can do this in ARIN Online through the Actions menu. If you do not have a valid letter of authority, you will need to verify your organization with ARIN. This can be done through the Bulk Whois feature on ARIN Online.

The Origin header is similar to the Referer header in that it is used to provide the security context for the origin request. The Origin header is added to a same-origin POST or DELETE request, a same-origin PUT or PATCH request, and to a cross-origin OPTIONS request. Similarly, it is not added to a non-cors request mode, such as a simple form post. It is also limited to 255 bytes. The Origin header is not used to disclose the path of the origin, and may be null. If it is null, the response will not contain any additional information. If a document’s Origin header does not contain an origin, it is not considered to be a cross-origin image.